(Reuters) - BioDelivery Sciences International Inc said the U.S. Food and Drug Administration had approved its opioid treatment for chronic pain, sending the drugmaker's shares up 23 percent in premarket trading on Monday.

Endo International Plc licensed the worldwide manufacturing and marketing rights to the treatment, Belbuca, from BioDelivery in 2012.

Belbuca is an opioid film patch and aims to treat patients with chronic pain who need round-the-clock treatment and for whom current alternatives do not suffice.

The patch is expected to be commercially available in the United States by the first quarter ending March in seven dosages, BioDelivery said.

Belbuca is placed on the inner lining of the cheek, leading to faster delivery of analgesic drug buprenorphine directly into the blood stream.

Buprenorphine has a lower abuse potential than most opioid medications. The Belbuca treatment can also prevent misuse through snorting or injecting as the film patch is difficult to crush or liquefy.

Given the lower possibilities of misuse as seen with buprenorphine, physicians can write a six-month prescription as opposed to writing one on a strict monthly basis.

"It (buprenorphine) is an easier drug to write," Laidlaw & Co Ltd analyst Jim Molloy said.

Since most of the drug is absorbed through the cheek and with little going through the digestive tract, Belbuca could potentially lead to lower constipation, a common side effect that most oral drugs are known to cause, Molloy said.

Molloy expects the treatment to rake in peak U.S. sales of about $450 million by 2018 for Endo, and about $80 million for BioDelivery. He said Belbuca accounts for $12 of his $17 price target on BioDelivery's shares.

The abuse of opioids, a class of drugs that include heroin and prescription painkillers, has long been a concern in the United States. An overdose of prescription painkillers can produce euphoric highs and even disrupt parts of the brain that control breathing.

The approval comes a little more than a month after the FDA staff flagged dosage concerns over Collegium Pharmaceutical Inc's opioid drug, Xtampza, and Purdue Pharma's fast-acting oxycodone painkiller.

The approval also triggers a $50 million milestone payment by Endo Pharmaceuticals to BioDelivery as part of a licensing agreement signed in 2012. The company will also receive royalties on U.S. net sales of the drug.

BioDelivery's shares, which closed at $5.28 on Friday on the Nasdaq, were at $6.50 before the bell.

(Reporting by Samantha Kareen Nair and Amrutha Penumudi in Bengaluru; Editing by Maju Samuel)